1. Technical Field
The present invention relates generally to induction devices. More particularly, the present invention relates to inductors and transformers.
2. Background Art
Traditional design and manufacture of induction devices, such as inductors and transformers, includes winding wires about a single core. In the past, the core has taken several forms, including a large toroid, an e-shaped armature and a cup core. The induction device resulting from such a core is generally box- or toroid-shaped and is not flexible. Consequently, the size of such an induction device frequently dictates the size of any device it is a part of. This is especially true for small and/or portable devices.
Many electrical devices use a power supply with a portable transformer. A popular type of power supply transformer takes the form of a box which may have prongs that plug into a wall outlet, or which may have a cord extending to a wall outlet and another cord extending to the device.
Box-type transformers provide several advantages. Electrical noise is isolated outside the device, rather than including the entire power supply within the device. Potentially dangerous voltage is also isolated outside the device. In addition, heat from the power supply is isolated away from the device.
However, such transformers also have several disadvantages. With very large box transformers, the heat generated may require a system for cooling. Often, the cooling system utilizes chemical coolants, such as freon, to cool the transformers. Such chemical coolants may be potentially dangerous to the environment. In addition, cooling systems may add to the cost of the power supply and/or the device(s) it is associated with. With smaller box transformers, the major disadvantage is inconvenience. For a portable device, a box transformer can be cumbersome to transport. A smaller box transformer may also be forgotten, rendering the device useless. Also, plug-in box transformers often fall out of the outlet due to their own weight. In addition, the box-type plug-in transformers may cover up other outlets.
Another type of transformer potentially solves the problems associated with box-type transformers. Transformers shaped like appliance powercords are being re-examined. Powercord transformers do not suffer from the disadvantages associated with box-type transformers. Heat is dissipated along the length of the transformer, rather than being concentrated in one place. Assuming the powercord transformer is attached to a portable device, it cannot be forgotten in transport. As a conventional plug can be used with the powercord transformer, other outlets are not covered up. In addition, since a powercord transformer's weight is dispersed over its length, the possibility of the plug falling out of the outlet is greatly reduced.
In the prior art, cord-like transformers, hereinafter referred to as powercord transformers, are highly inefficient and may not work. One example of a powercord transformer is described in U.S. Pat. No. 2,436,742, issued to Bussey. Disclosed there is a combination transformer and powercord. However, the Bussey powercord transformer, referred to therein as a line cord transformer, fails to provide a reliable return path for the magnetic flux produced in the single core. Presumably, although not disclosed therein, Bussey utilizes air as a return flux path to induce a voltage in the secondary winding. Given that air has a permeability (.mu.) of 1, it is a distinct possibility that no voltage or an insufficient voltage will be induced in the secondary winding.
In addition to the restrictions resulting from traditional induction device design, traditional methods of manufacture are inherently difficult to implement. Automation of the manufacturing process is often expensive and impractical, since traditional coil winding methods of manufacture require complex mechanical operations.
Thus, a need exists for a new induction device design, as well as a method of manufacture that is easily implemented.